Iteration for String (Crossed) method

Hello, I currently have written code for Newton method. However, I need to change it to String or also known as Crossed method and I have no idea how to do that. My current one is below:

x0 = a; dx = eps;
  atlikta = 0;           
while ~atlikta           
  x = x0;
  f0 = eval(f);          
  x = x + dx;
  fd = eval(f);          
  df = (fd - f0) / dx;   
  x1 = x0 - f0 / df;     
if abs(x1 - x0) < eps
  atlikta = 1;           
else
  x0 = x1;               
end                      
spr = x1;
end                      

[Rik]

Even in Octave you shouldn't need eval here.

Also, this is completely undocumented code, and you don't explain what changes you want to make. It sounds to me like you need to implement an entirely different algorithm, but you don't explain the differences, nor what you have tried.